/*
 * Copyright (c) 2009, Hamish Morgan. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the University of Sussex nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package locusts.server.behaviours;

import java.util.List;


import javax.vecmath.Vector2d;
import locusts.common.entities.Actor;
import locusts.common.entities.EntityType;

/**
 * Steering to match the heading of neibouring vehicles.
 * 
 * @author Hamish Morgan Morgan
 */
public class FlockAlignment extends AbstractFlockBehaviour {

    public FlockAlignment(double weight, EntityType flockType,
            double minDistance, double maxDistance, double maxAngle) {
        super(weight, flockType, minDistance, maxDistance, maxAngle);
    }

    public FlockAlignment(double weight, EntityType flockType) {
        super(weight, flockType);
    }

    public FlockAlignment(EntityType flockType) {
        super(flockType);
    }

    // Alignment: steer towards the average heading of local
    // flockmates
    public final Vector2d getSteering(final Actor boid) {

        final Vector2d steering = new Vector2d();
        List<Actor> neighbors = getNeighbors(boid);

        if (neighbors.size() == 0)
            return steering;
        if (getWeight() == 0d)
            return steering;

        for (Actor other : neighbors) {
            if (!other.isAlive())
                continue;
            steering.x += other.getVX();
            steering.y += other.getVY();
//            steering.add(other.getVelocity());
        }

        steering.scale(1f / neighbors.size());

        double c = 1f;
        if (steering.x > 0f)
            steering.x = 1f - c / (steering.x + c);
        else if(steering.x < -0f)
            steering.x = -1f - c / (steering.x - c);
        if (steering.y > 0f)
            steering.y = 1f -  c / (steering.y + c);
        else if(steering.y < -0f)
            steering.y = -1f - c / (steering.y - c);

        steering.scale((double) getWeight());
        return steering;
    }

    

}
